Classifications

• • C—CHEMISTRY; METALLURGY
  • C07—ORGANIC CHEMISTRY
  • C07C—ACYCLIC OR CARBOCYCLIC COMPOUNDS
  • C07C201/00—Preparation of esters of nitric or nitrous acid or of compounds containing nitro or nitroso groups bound to a carbon skeleton
  • C07C201/06—Preparation of nitro compounds
  • C07C201/08—Preparation of nitro compounds by substitution of hydrogen atoms by nitro groups

Definitions

• the present invention relates to a process for preparing m,m'-dinitrobenzophenone which comprises reacting benzophenone with nitric acid in oleum.
• a product When benzophenone is reacted with nitric acid, a product can be obtained containing an isomeric mixture of dinitrobenzophenones, including o,o'-, o,m'-, m,m'-, m,p'- and p,p'-dinitrobenzophenones, which, in turn, can be subjected to hydrogenation to obtain an isomeric mixture of the corresponding diaminobenzophenones.
• the latter mixture can be reacted with 3,4,3',4'-benzophenone tetracarboxylic dianhydride (BTDA) to obtain a polyimide resin.
• BTDA 3,4,3',4'-benzophenone tetracarboxylic dianhydride
• benzophenone can be reacted with nitric acid to obtain a product containing an isomeric mixture of dinitrobenzophenones predominating in m,m'-dinitrobenzophenone, while substantially reducing the content of the isomers containing an ortho-nitro substituent with virtual disappearance of the o,o'-dinitrobenzophenone, by a process wherein benzophenone is reacted with nitric acid in oleum while maintaining critical weight ratios of benzophenone, sulfuric acid and sulfur trioxide in the feed.
• the critical weight ratio of benzophenone, sulfuric acid (as 100 percent sulfuric acid) and sulfur trioxide must be in the range of about 1:3:1 to about 1:25:5, but preferably in the range of about 1:2:2 to about 1:15:4.
• the sulfuric acid and sulfur trioxide employed can be satisfied by the use of oleum.
• oleum we mean to include concentrated sulfuric acid containing sulfur trioxide.
• the amount of sulfur trioxide, on a weight basis relative to the total weight of sulfuric acid and sulfur trioxide, will be in the range to satisfy the critical weight ratios defined above, for example, in the range of about five to about 65 percent, preferably about 10 to about 35 percent.
• Oleum suitable for use herein can be prepared, for example, by adding gaseous or liquid SO 3 to concentrated sulfuric acid. It is believed that sulfur trioxide when dissolved in, or added to, sulfuric acid readily forms H 2 S 2 O 7 and higher polysulfuric acids [R. Gillespie, J. Chem. Soc., 2493 (1950)].
• benzophenone, nitric acid, sulfuric acid and sulfur trioxide are brought together, with the weight ratios of benzophenone, sulfuric acid and sulfur trioxide being within the critical ranges defined above.
• the amount of nitric acid is not critical and should be sufficient, stoichiometrically, to place one nitro group on each of the rings of the benzophenone being treated. To assure substantially complete reaction, amounts in excess of those required stoichiometrically to obtain dinitrobenzophenones can be used, for example, up to about 10 weight percent, or even higher.
• concentration of the nitric acid used can vary over a wide range, for example from about 50 to about 100 weight percent aqueous nitric acid, preferably from about 67 to about 95 weight percent aqueous nitric acid.
• the reaction can be carried out for example by stirring the reaction mixture while heating the same in a temperature range of about 5° to about 120° C., preferably about 10° to about 90° C., for about 10 minutes to about 120 hours, or even longer, preferably for about one-half to about 24 hours.
• the process is carried out in a plurality of stages. In a first stage, for example, the temperature is maintained in a range of about 5° to about 50° C., preferably about 10° to about 30° C., for about 10 minutes to about 10 hours, preferably for about one-half to about eight hours.
• reaction mixture In a second stage the reaction mixture is maintained in the temperature range of about 20° to about 120° C., preferably about 50° to about 90° C., for about one-half to about five hours, preferably about one to about three hours.
• the pressure is not critical and elevated pressures up to about 100 pounds per square inch gauge (about 0.7 MPa), or even higher, can be used, although atmospheric, or ambient, pressure is preferred.
• the dinitrobenzophenones can be recovered from the reaction mixture in any suitable or convenient manner.
• the reaction mixture can be poured over ice and the resulting slurry can be subjected to filtration.
• the resulting filter cake comprising the isomeric mixture of dinitrobenzophenones, can be washed with an alkaline solution, such as sodium hydroxide, potassium hydroxide or ammonium hydroxide, and water, to remove possible contaminating materials therefrom, such as residual nitric acid, sulfuric acid, sulfur trioxide, organic acids, phenolics, etc., and dried.
• the filter cake will contain substantially high amounts of meta-dinitrobenzophenones, particularly m,m'-dinitrobenzophenones.
• the weight ratio of m,m'- to m,p'-dinitrobenzophenones will be in the range of about 90:10 to about 96:4, generally about 92:8 to about 94:6.
• the filter cake will contain no appreciable amounts of o,o'- or p,p'-dinitrobenzophenones.
• the weight percent of o,m'-dinitrobenzophenone will be substantially reduced and will amount, for example, to about 0 to about 15 weight percent, generally in the range of 0 to about five weight percent, of the filter cake, but, most preferably, about 0 to about two.
• the reaction product at the end of the reaction period always contains sulfur trioxide, for example, in amounts in excess of about four weight percent, and as high as about 20 weight percent, or even higher, but generally about 10 to about 15 weight percent, based on the weight of the reaction product.
• Example II The product was cooled and worked up as in Example I, resulting in the production of 163.7 grams of dinitrobenzophenones, essentially 100 percent yield. Analysis of the product by HPLC showed the following: 2.5 weight percent o,o'-dinitrobenzophenone, 20.6 weight percent o,m'-dinitrobenzophenone, 65.2 weight percent m,m'-dinitrobenzophenone, 11.7 weight percent m,p'-dinitrobenzophenone and ⁇ 0.1 weight percent p,p'-dinitrobenzophenone.
• a nitrating mixture was prepared by adding 165 grams of 90 weight percent aqueous nitric acid over a period of 30 minutes to 570 grams of well stirred oleum containing concentrated sulfuric acid and 22.5 weight percent sulfur trioxide while maintaining the temperature of the resulting mixture during the stirring procedure at about 10° to about 15° C.
• Two hundred grams of benzophenone were gradually dissolved over a period of 60 minutes in 1900 grams of oleum containing 22.5 weight percent sulfuric acid while maintaining the temperature of the resulting mixture at about 10° to about 20° C. With vigorous stirring and cooling the nitrating mixture of acids prepared above was gradually added to the benzophenone mixture over a period of 1.5 hours at about 10° to about 15° C.
• Example III The resulting mixture was allowed to warm to 25° C. and was held at this temperature, with stirring, for a period of 30 minutes. An aliquot sample was taken up and analyzed for its isomeric dinitrobenzophenone content. The results are tabulated in Table I below under Example III (a). The remainder of the reaction mixture was heated to 70° C., at which point another sample was taken and analyzed. The results are tabulated in Table I as Example III(b). Reaction was continued with the remainder of the reaction mixture at 70° C. for an additional hour. Samples were taken at the end of each one-half hour and analyzed. These results are also tabulated in Table I as Examples III(c) and III(d), respectively.
• the resulting reaction product was cooled, poured over 2000 grams of cracked ice-water mixture and filtered.
• the recovered solids were washed twice, each time with 1000-milliliter portions of water, then with 1000 milliliters of 10 weight percent aqueous sodium hydroxide and finally twice, each time with 1000 milliliters of water, until the washings were found to be neutral.
• the solids were then dried in a vacuum oven at 100° C. for 16 hours, resulting in the recovery of 252 grams of dinitrobenzophenones, corresponding to a yield of 84 percent.
• Table I shows the uniqueness of the process defined and claimed herein.
• the amount of m,m'-dinitrobenzophenone was below the amount desired and the amount of dinitrobenzophenones containing an ortho nitro substituent was exceedingly high.
• sulfur trioxide was present in the feed in each of Examples IV, V and VI, the weight ratio of benzophenone, sulfuric acid and sulfur trioxide in the feed was not in the critically-defined range, and therefore only relatively slight increases in the amount of m,m'-dinitrobenzophenone and only relatively slight decreases in o,m'-dinitrobenzophenone content was noted.
• Example III it is shown that as the reaction progresses at the higher temperatures, the amount of o,m'-dinitrobenzophenone is greatly decreased, resulting in a final product wherein the percentage of m,m'-dinitrobenzophenone is greatly enhanced. That comparable results can be obtained by maintaining the reaction mixture at a lower temperature level but for extended periods of time is shown below in Example XI.

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• 1981
  • 1981-03-11 US US06/242,691 patent/US4361704A/en not_active Expired - Fee Related
  • 1981-11-16 CA CA000390155A patent/CA1156263A/en not_active Expired
  • 1981-12-08 EP EP81305800A patent/EP0059813B1/en not_active Expired
  • 1981-12-08 DE DE8181305800T patent/DE3169609D1/de not_active Expired
• 1982
  • 1982-02-18 JP JP57023687A patent/JPS57150637A/ja active Granted

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